Delirium, Dementia, and Amnesia in Emergency Medicine Workup

Updated: Apr 07, 2017
  • Author: Paul S Gerstein, MD; Chief Editor: Gil Z Shlamovitz, MD, FACEP  more...
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Workup

Laboratory Studies

Laboratory studies may be helpful for ruling in or excluding specific diagnoses that cause delirium or a dementia-like presentation. Many of these tests may not be immediately available to the ED physician including vitamin levels, Venereal Disease Research Laboratory (VDRL) test, and certain thyroid function studies.

Oxygen saturation, or ABG with carbon monoxide level, may be diagnostic. CBC, electrolytes, blood glucose, BUN and creatinine should be checked. In older patients, consider vitamin B-12 and folate levels. Consider calcium level, magnesium level, liver function tests (LFTs), serum ammonia, and prothrombin time (PT). Consider VDRL and/or fluorescent treponemal antibody absorption (FTA-ABS) test to help rule out neurosyphilis (see cerebrospinal fluid [CSF] studies below). Urinalysis is also indicated.

When alcohol, drugs, and/or toxins are suspected, consider the following:

  • Serum ethanol, salicylate, acetaminophen, carbon monoxide, and other specific drug or toxin levels as indicated
  • Comprehensive drug analysis of urine

In a suspected endocrine emergency, the following are required:

  • A bedside fingerstick blood glucose determination followed by serum glucose and serum acetone
  • Thyroid-stimulation hormone (TSH), possibly thyroid panel
  • Serum cortisol
  • Serum calcium, phosphorus, and parathyroid levels

In suspected CNS infection, the following may be ordered:

  • Lumbar puncture may be done for CSF studies, including cryptococcal antigen, Lyme disease and VDRL.
  • CT scan of head should be done before lumbar puncture to rule out toxoplasmosis or abscess, especially in patients with HIV who present with headache.
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Imaging Studies

A head CT scan without intravenous (IV) contrast should be obtained if CNS infection, trauma, or a cerebral vascular accident (CVA) is suspected. A CT scan is excellent for detecting acute hematomas and most subarachnoid hemorrhages (SAH) but is most accurate early in the course. Follow-up lumbar puncture may be needed to rule out SAH.

One study found a high prevalence (41%) of abnormal CT scan findings in patients with acute mental status changes in the ED. Eight clinical predictors were significantly associated with an abnormal scan, including diastolic blood pressure of more than 80 mm Hg, focal weakness, a Glasgow Coma Score of less than 15, antiplatelet use, upgoing plantar response, headache, anticoagulant use, and dilated pupils. [9]

Although not typically part of the workup in the ED, a brain MRI may be considered if readily available and the need confirmed by neurologist and/or radiologist. MRI helps distinguish between Alzheimer disease and vascular causes of dementia. The MRI may show subtle signs of stroke missed on CT and is the imaging modality of choice for multiple sclerosis. An example of MRI in a patient with moderate Alzheimer disease is shown in the image below.

Coronal T1-weighted MRI scan in a patient with mod Coronal T1-weighted MRI scan in a patient with moderate Alzheimer disease. Brain image reveals hippocampal atrophy, especially on the right side.

Plain abdominal radiographs may reveal swallowed bags that contain drugs of abuse ("body packing") or radiodense substances such as iron tablets.

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Other Tests

An ECG may be performed to search for myocardial infarction or atrial fibrillation with rapid ventricular response. Low voltages, as seen in hypothyroidism and pericardial effusion, may give a clue to the etiology. Look for tachycardia, widened QRS, or prolonged QT interval, which suggest tricyclic overdose.

A postmortem examination of the brain is currently the only way to positively diagnose the various dementing illnesses.

A blood test for apolipoprotein E (ApoE) subtype e4 is still under study, but it promises to greatly enhance diagnostic accuracy for AD.

Researchers at the Stanford University School of Medicine developed a blood test that may someday be a step toward predicting AD 2-6 years in advance of onset. The test identifies changes in certain blood proteins that cells use to convey messages to one another and has a 90% positive predictive value. [10] Lack of test specificity has been a stumbling block to this potential diagnostic tool.

Testing vitamin B-12 levels and thyrotropin is useful as part of a dementia workup.

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Procedures

Lumbar puncture to obtain CSF for analysis should be considered in certain circumstances, including the following:

  • To rule out SAH not seen on CT scan
  • To diagnose CNS infections such as encephalitis or meningitis
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